Good stuff, mate. The composing suits the title. My only suggestion: work those volume sliders a bit!
The opening piano has some low notes so it's a pretty powerful instrument in the piece; "Underwater" implies a bit of peacefulness so by the time the electric piano comes in, maybe have that faded out most of the way. The choir/string chords could also swell up and down a bit, maybe getting a bit louder on the 4th chord was has a "bigger" sound anyway.
Yeah, I don't really like critiquing things because people are usually happy with their work, but the notes you wrote are A-OK, so now I just think the dynamics in how they're used can make a big difference.